I *think* I'm going through this right now. It is totally perplexing to me.
My quick story: I know a woman who shares a lot in common with me (shows, sense of humor, politics, age, etc.) but she excludes me from everything.
Beyond feeling personal at this point, it feels intentional.. and I'm at a total loss as to what it's about despite us going to Happy Hour twice to try to hash out what the issue was. I always walked away from those drinks thinking everything was fine, only to find out a week later she invited a bunch of mutual friends to stuff and left me off the list.
I really beat myself up over this (especially as other people seemed to side with her), but since no one has ever offered me an explanation for what's happening- I've decided I need to let it go and learn from this: believe people when they show you who they are.